linux-kernel - [PATCH 2/8] tty: fix return value for unsupported ioctls

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Date:   Wed,  7 Apr 2021 11:52:02 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jiri Slaby <jirislaby@...nel.org>, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>
Subject: [PATCH 2/8] tty: fix return value for unsupported ioctls

Drivers should return -ENOTTY ("Inappropriate I/O control operation")
when an ioctl isn't supported, while -EINVAL is used for invalid
arguments.

Fix up the TIOCMGET, TIOCMSET and TIOCGICOUNT helpers which returned
-EINVAL when a tty driver did not implement the corresponding
operations.

Note that the TIOCMGET and TIOCMSET helpers predate git and do not get a
corresponding Fixes tag below.

Fixes: d281da7ff6f7 ("tty: Make tiocgicount a handler")
Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/tty/tty_io.c       | 10 +++++-----
 include/linux/tty_driver.h |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index ebcde1f96adb..7738514a15fe 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2529,14 +2529,14 @@ static int send_break(struct tty_struct *tty, unsigned int duration)
  *	@p: pointer to result
  *
  *	Obtain the modem status bits from the tty driver if the feature
- *	is supported. Return -EINVAL if it is not available.
+ *	is supported. Return -ENOTTY if it is not available.
  *
  *	Locking: none (up to the driver)
  */
 
 static int tty_tiocmget(struct tty_struct *tty, int __user *p)
 {
-	int retval = -EINVAL;
+	int retval = -ENOTTY;
 
 	if (tty->ops->tiocmget) {
 		retval = tty->ops->tiocmget(tty);
@@ -2554,7 +2554,7 @@ static int tty_tiocmget(struct tty_struct *tty, int __user *p)
  *	@p: pointer to desired bits
  *
  *	Set the modem status bits from the tty driver if the feature
- *	is supported. Return -EINVAL if it is not available.
+ *	is supported. Return -ENOTTY if it is not available.
  *
  *	Locking: none (up to the driver)
  */
@@ -2566,7 +2566,7 @@ static int tty_tiocmset(struct tty_struct *tty, unsigned int cmd,
 	unsigned int set, clear, val;
 
 	if (tty->ops->tiocmset == NULL)
-		return -EINVAL;
+		return -ENOTTY;
 
 	retval = get_user(val, p);
 	if (retval)
@@ -2606,7 +2606,7 @@ int tty_get_icount(struct tty_struct *tty,
 	if (tty->ops->get_icount)
 		return tty->ops->get_icount(tty, icount);
 	else
-		return -EINVAL;
+		return -ENOTTY;
 }
 EXPORT_SYMBOL_GPL(tty_get_icount);
 
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 61c3372d3f32..2f719b471d52 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -228,7 +228,7 @@
  *
  *	Called when the device receives a TIOCGICOUNT ioctl. Passed a kernel
  *	structure to complete. This method is optional and will only be called
- *	if provided (otherwise EINVAL will be returned).
+ *	if provided (otherwise ENOTTY will be returned).
  */
 
 #include <linux/export.h>
-- 
2.26.3